1. Field of the Invention
The present invention relates to a fundus camera and an ophthalmologic image processing apparatus. More particularly, the present invention relates to a technique useful for gradation conversion of an eye fundus image.
2. Description of the Related Art
When an image of a fundus of a subject's eye is captured using a fundus camera, it is useful if both an optic papilla portion and a macular portion, which are the brightest and the darkest portions in a fundus image, can be observed at the same time.
Japanese Patent Application Laid-Open No. 2000-107133 discusses a fundus camera that captures an image of a subject's eye using an imaging unit by alternately changing an intensity of light emitted from a photographing light source.
Japanese Patent Application Laid-Open No. 2003-52639 discusses a fundus camera that generates a high-contrast image for each region of interest, such as a macular portion or an optic papilla portion, in one image-capturing operation of a fundus according to a setting value for each region, and stores the generated image.
However, if the conventional fundus camera is used to capture one eye fundus image including both the optic papilla portion being the brightest portion and the macular portion being the darkest portion in the fundus image, since an image sensor does not provide a satisfactory dynamic range, the macular portion will be underexposed if the exposure of the optic papilla portion is appropriate. On the other hand, overexposure of the optic papilla portion occurs if the exposure of the macular portion is appropriate.
If a fundus camera such as the one discussed in Japanese Patent Application Laid-Open No. 2000-107133 is used, an operator needs to flash the photographing light source twice in capturing an image.
If a fundus camera such as the one discussed in Japanese Patent Application Laid-Open No. 2003-52639 is used, the operator needs to look at two different images when the operator views the optic papilla portion and the macular portion.